<template>
    <div id="Application">
      <!-- 游戏区域 -->
      <div class="container">
        <!-- 底部挡板 -->
        <div class="board" :style="{left: boardX + 'px'}"></div>
        <!-- 弹球 -->
        <div class="ball" :style="{left: ballX+'px', top: ballY+'px'}"></div>
        <!-- 游戏结束提示 -->
        <h1 v-if="fail" style="text-align: center;">游戏失败</h1>
      </div>
    </div>
  </template>
  
  <script>
  export default {
    data() {
      return {
        // 控制挡板位置
        boardX: 0,
        // 控制弹球位置
        ballX: 0,
        ballY: 0,
        // 控制弹球移动速度
        rateX: 0.1,
        rateY: 0.1,
        // 控制结束游戏提示的展示
        fail: false
      }
    },
    mounted() {
      // 添加键盘事件
      this.enterKeyup();
      // 随机弹球的运动速度和方向
      this.rateX = (Math.random() * 0.5 + 0.1);
      this.rateY = (Math.random() * 0.5 + 0.1);
      // 开启计数器，控制弹球移动
      this.timer = setInterval(() => {
        // 到达右侧边缘进行反弹
        if (this.ballX + this.rateX >= 440 - 30) {
          this.rateX *= -1;
        }
        // 到达左侧边缘进行反弹
        if (this.ballX + this.rateX <= 0) {
          this.rateX *= -1;
        }
        // 到达上侧边缘进行反弹
        if (this.ballY + this.rateY <= 0) {
          this.rateY *= -1;
        }
        this.ballX += this.rateX;
        this.ballY += this.rateY;
        // 失败判定
        if (this.ballY >= 440 - 30 - 10) {
          // 挡板接住了弹球，进行反弹
          if (this.boardX <= this.ballX + 30 && this.boardX + 80 >= this.ballX) {
            this.rateY *= -1;
          } else {
            // 没有接住弹球，游戏结束
            clearInterval(this.timer);
            this.fail = true;
          }
        }
      }, 2);
    },
    methods: {
      // 控制挡板移动
      keydown(event) {
        if (event.key === "ArrowLeft") {
          if (this.boardX > 10) {
            this.boardX -= 20;
          }
        } else if (event.key === "ArrowRight") {
          if (this.boardX < 440 - 80) {
            this.boardX += 20;
          }
        }
      },
      enterKeyup() {
        document.addEventListener("keydown", this.keydown);
      }
    }
  }
  </script>
  
  <style scoped>
  body {
    margin: 0;
    padding: 0;
  }
  .container {
    position: relative;
    margin: 0 auto;
    width: 440px;
    height: 440px;
    background-color: blanchedalmond;
  }
  .ball {
    position: absolute;
    width: 30px;
    height: 30px;
    left: 0px;
    top: 0px;
    background-color: orange;
    border-radius: 30px;
  }
  .board {
    position: absolute;
    left: 0;
    bottom: 0;
    height: 10px;
    width: 80px;
    border-radius: 5px;
    background-color: red;
  }
  </style>
  